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New Device Would Detect THC in Driver’s System

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graphic depicting a driver stoned on marijuana

Image courtesy National Institute on Drug Abuse

Washington State University (WSU) researchers are working on a portable marijuana breath test device that would be similar to the blood alcohol breath (BAC) tests police use, as Darren Whitehead writes for KUSA-TV Denver in an article appearing in USA Today. Police in Colorado and Washington state, where recreational marijuana is legal, have been relying on blood tests to find out if a driver has been smoking or otherwise consuming pot, Whitehead writes.

Police in states where recreational marijuana is legal — including Alaska and Oregon as well as Colorado and Washington — and police in many states where pot is legal for medical use have also been using traditional standardized field sobriety tests to test impaired drivers for marijuana, writes David Knowles for Bloomberg Politics. So far, no portable tool similar to the BAC breathalyzer exists that can determine whether a driver has marijuana in his or her system, writes Melissa Santos for The New Tribune in an article appearing in The Seattle Times.

The device that WSU chemistry professor Herbert Hill and a doctoral student have been working on would make the detection process easier for police, Whitehead writes. The marijuana breathalyzer will detect THC, which is the psychoactive element of marijuana, Knowles writes. A study done in 2012 found that only 30% of drivers under the influence of THC failed the standard sobriety tests, Knowles notes, adding that blood test results can take up to 24 hours. Hill hopes the THC breathalyzer will provide police with a more immediate way to detect the presence of THC in a person’s system.

Knowles reports that in the first full year after Washington legalized the recreational use of marijuana, the number of drivers testing positive for marijuana in their system rose by 25%. He writes that the Colorado Department of Transportation (CDOT) warns on its website that driving under the influence of marijuana can result in a DUI charge.

Knowles quotes the CDOT:

Marijuana affects reaction time, short-term memory, hand-eye coordination, concentration and perception of time and distance. Getting high and getting behind the wheel of a car will get you arrested for a DUI – this law hasn’t changed with the legalization of marijuana in January 2014.

Hill and his researcher plan to complete lab testing of a prototype marijuana breath test this month, and will begin testing the device on humans next year, Whitehead writes. After that, they will test the THC breathalyzer in the field.

At first, the THC device will not be able to specify the amount of THC in a person’s system, but only that the psychoactive substance is in his or her system, Hill told Santos. The device should “at least initially” lower the false positives that police encounter in their testing, he said; as a result, police would have more confidence in making DUI arrests. However, after a driver is found to be impaired, law enforcement agencies would need to do follow-up testing for use as evidence in court, Santos writes.


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